System for primer actuation of bolt

ABSTRACT

1. For use with a gun having a firing pin, a cartridge having a hollow casing adapted to contain a powder charge and having a base at the rear end, said base having an axially extending aperture, a primer mounted in the forward portion of said aperture, retaining means for limiting movement of said primer in a forward direction, a piston slideably mounted in the rearward portion of said aperture behind said primer, said piston having a surface facing said primer, a forwardly extending projection on said surface, said piston adapted to be driven forward by said firing pin causing said projection to strike said primer and deform the same against the resistance of said retaining means, the impact of said projection upon said primer causing initiation of the latter and ignition of the charge whereby propellent gases are produced which act upon said primer and said surface, said piston being rearwardly accelerated independently of said primer by the action of the propellent gases upon said surface to thereby impart a rearward acceleration to said firing pin.

United States atent [1 1 Barr et al.

[75] Inventors: lrwin R. Barr, Lutherville; Nicholas J. La Costa, Kingsville, both of Md.

[73] Assignee: Aircraft Armaments, Inc.,,

Cockeysville, Md.

[22] Filed: Jan. 7, 1959 [21] Appl. No.: 785,525

[52] U.S. Cl 89/159, 89/179, 102/38, 102/45 [51] Int. Cl. .L. F4ld 5/04, F42b 5/02 [58] Field of Search 102/38, 44, 45, 46, 39, 102/40, 41; 89/156, 159, 179

[56] References Cited UNITED STATES PATENTS 381,264 4/1888 Lorenz 89/179' 624,145 5/1899 Young 89/179 624,146 5/1899 Young 102/38 2,592,623 4/1952 Turnbull 102/38 2,630,067 3/1953 McWhorter 102/38 2,777,391 l/l957 McNally 102/38 SYSTEM FOR PRIMER ACTUATION OF BOLT Primary ExaminerRobert F. Stahl Attorney, Agent, or FirmReginald F. Pippin, Jr.

EXEMPLARY CLAIM 1. For use with a gun having a firing pin, a cartridge having a hollow casing adapted to contain a powdercharge and having a base at the rear end, said base having an axially extending aperture, a primer mounted in the forward portion of said aperture, retaining means for limiting movement of said primer in a forward direction, a piston slideably mounted in the rearward portion of said aperture behind said primer, said piston having a surface facing said primer, a forwardly extending projection on said surface, said piston adapted to be driven forward by said firing pin causing said projection to strike said primer and deform the same against the resistance of said retaining means, the impact of said projection upon said primer causing initiation of the latter and ignition of the charge whereby propellent gases are produced which act upon said primer and said surface, said piston being rearwardly accelerated independently of said primer by the action of the propellent gases upon said surfaceto thereby impart a rearward acceleration to said firing pin.

11 Claims, 5 Drawing Figures PATENTED E 3,855,300

sum 1 or 2 IRWIN R. BARR NICHOLAS J. LA COSTA IN V EN TORS Q ZLIQQ. M2

A T TORNE Y PAIENTEQ EHZ :wasoo SHCET 2 OF 2 IRWIN R. BARR NICHOLAS J. LA COSTA IN V EN TORS A T TORNE Y SYSTEM FOR PRIMER ACTUATION OF BOLT This invention relates to cartridges for use in firearms and, more particularly, to cartridges of the class used in automatic and semi-automatic firearms which operate on the principle of primer set-back.

Automatic and semi-automatic firearms which use the principle of gas operation are well known to those skilled in the art. In such firearms, propellent gases are tapped from the barrel into a gas cylinder attached thereto where they can act on a piston connecting with the breech mechanism. Because of the enormous pressure of the gases, the piston tends to apply heavy acceleration loads to the moving parts of the breech mechanism. A lower working pressure of reasonable value is obtained by locating the gas port remote from the breech portion of the barrel where the available gas pressure is reduced, and by making the port area small to throttle the gases entering the cylinder. By employing these expedients, very successful firearms have been designed. I

An inherent problem in any gas-operated firearm arises because of the hole bored in the barrel to form the gas port. The hole is difficult to clean and is always a point where rust and corrosion are likely to start. Another problem in a gas-operated firearm that is to be 7 carried arises because of the additional size and weight of the gas cylinder, piston and associated linkages. It is desirable to make these components as light as possible to reduce their weight, but heavy enough to have sufficient inertia to carry through the requisite movement after the gas pressure is gone. Obviously these requirements are in conflict, with the result that in order to be given sufficient energy to actuate the breech mechanism, the piston must receive a violent impact from the gases. This drives the piston rearwardly at a very great velocity. Such action is conducivje to high breakages and requires increased maintenance.

Automatic and semi-automatic firearms which use the principle of primer set-back, are also well known in the art and are known to be lighter, less complex and require less maintenance than gas-operated firearms. In primer set-back firearms, the cartridge is designed to allow its primer to move slightly in the cartridge case under the influence of the pressure of the gas generated when the gun is fired. In so doing, the energy given to the primer is transferred through the firing pin to an actuator which opens the breech and extracts the cartridge while charging a spring. The spring then acts to reload the firearm.

Recalling that a primer is a thin-walled cup-shaped configuration opening toward the interior of the cartridge, it is evident that the pressure of the propellent gases acts not only upon the bottom of the cup to impart movement to the primer, but also upon the side walls causing them to obturate against the interior of the cartridge. While this obturation is desirable and seals the gases interior to the cartridge, a considerable amount of the force available to impart movement to the primer may be required to overcome the frictional forces arising from obturation. Thus, the resultant force useful to impart energy to the firing pin may be significantly reduced from the force actually available.

There is a definite limit then to the amount of energy available to the firing pin by way of primer set-back, particularly when it is realized that increasing the gas pressure to increase the force on the cup bottom is accompanied by a corresponding increase in the resisting frictional forces, since the frictional forces obtained are almost directly proportional to the gas pressure.

In order to achieve breech actuation without relying upon movement of the primer, movable pistons may be inserted in the base of the cartridge around the primer. When the primer is fired to ignite the charge in the cartridge, the propellent gases thereby generated act upon the pistons driving them rearwardly into contact with a slideable tappet member which in turn acts upon the firing pin to effect operation of the breech mechanism. Because the pistons are spaced from the axis of the cartridge, movement of one piston at a speed greater than that of the others would tend to cock the sliding tappet member and would also decrease the energy able to be imparted to the tappet. v

In some instance, it may be desirable to impart energy to the firing pin simultaneous with firing of the primer or at least prior to ignition of the main charge. Since in the conventional cartridge, piston actuation depends upon ignition of the main charge, such cartridge is not adaptable for the above-described use.

After piston movement is accomplished by ignition of the main charge, and the tappet is thrust rearwardly, thepistons project beyond the base of the cartridge.

Such projections may interfere with the cartridge extraction mechanism. More important,.however, is the fact that the tappet, being spaced from the cartridge base after firing, no longer supports the primer cup. As a result, it is apt to be extruded by the gas pressure into the firing pin aperture in the tappet member.

Much effort has been expended to contribute a cartridge of the class described inwhich the energy available to the firing pin is not limited in the manner set forth above, but so far as is known, no successful device of the class described has yet been contributed to the art, and the problems here outlined remain unsolved. It is an object of this invention to contribute a cartridge of the class described in which the provision of a movable piston separate from the primer does not result in limitingthe force applied to the firing pin, in the possibility of extruding the primer, or in having parts which extend from the cartridge after firing.

As a feature of this invention, whereby the objects thereof are achieved, a primer piston separate fromthe primer is positioned behind and in alignment with the primerfThe firing pin engages the piston driving it forward further into the cartridge causing it to strike and initiate the primer. The gases generated may be allowed to act directly upon the piston driving it and the firing pin rearwardly. By adjusting the area of the piston, any amount of energy may be given to the piston during its short rearward stroke. Such. energy is transferred directly to the firing pin.

The more important features of this invention have thus been outlined rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contribution to the art may be better appreciated. There are, of course, ad-

ditional features of the invention that will be described hereinafter and which will also form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other apparatus for carrying out the several purposes of this invention. It is important, therefore, that the claims to be granted herein shall be of sufficient breadth to prevent the appropriation of this invention by those skilled in the aft.

FIG. 1 is a cross-sectional view of a firearm into which is inserted a cartridge made in accordance with this invention and showing the firing pin about to strike the primer configuration.

FIG. 2 is a view similar to FIG. 1 but with the firing pin striking the primer configuration.

FIG. 3 is a view similar to FIG. 2 but with the firing pin shown thrust rearward in response to firing of the primer configuration, and acting to unlock the breech lock.

FIG. 4 is a view showing the beginning of the extraction of the fired round.

FIG. 5 is a modification of the primer configuration shown inFIGS. l 4.

Referring now to the drawings, there is shown in FIG. 1 a firearm having a barrel 11, a barrel extension 12 screwed thereto, and a bolt receiver 13 screwed to extension 12. Barrel 11 has chamber 14 therein; and extension 12 has a plurality of locking lugs 15, spaced from the breech end 16 of barrel 12, which form recess 17 into which spaced locking projections 18 of bolt 19 are engaged. Projections 18 are engageable behind lugs and securely position cartridge 20 in chamber 14 because face 21 on bolt 19 engages the rear portion 22 of cartridge 20.

Bolt 19 has cylindrical recess 23 in the rearward portion thereof which interconnects with face 21 by way of tapered recess 24 and cylindrical aperture 25. Cam slot 26 opens to recess 23 and has a portion 27 parallel to the axis of firearm l0 and at one end, a curved portion 28. Engaged in slot 26 is follower 29 of firing pin 30 which itself is generally cylindrical in shape and reciprocally mounted in recess 23 in bolt 19. At the forward end of firing pin 30 is taper 31 and tip 32. The shape of taper 31 and tip 32 is such taht firing pin 30 is movablefrom a forward position shown in FIG. 2 with tip 31 projecting beyond face 21 and taper 31 engaged with recess 24, to a rearward position suggested by'FIG. 4. Firing pin 30 is allowed to reciprocate without any rotation in a conventional manner. As a result initial rearward movement of follower 29 in portion 27 of slot 26, does not have any effect on bolt 19; as follower 29 engages portion 28 of slot 26, continued rearward movement causes rotation of bolt 19 such that projections 18 are withdrawn from behind lugs 15; during final rearward movement of firing pin 30, there is an engagement between pin 30 and bolt 19 such that the bolt and pin move as a unit as shown in FIG. 5. Flanges 33 on projections 18 are engageable over extractor rim 34 of cartridge 20 to extract the cartridge during the final rearward move above described.

Cartridge 20 is generally cylindrical in shape having a hollow casing 35 and a base 36 at one end upon which extractor rim 34 is formed. Connecting the interior of casing 35 with the rearmost face of base 36 is a centrally located aperture 37 which may be countersunk adjacent the rearmost face 22. Primer configuration 38 is mounted in recess 36' of casing 36. Configuration 38 includes a percussion primer 39 in the forward portion of recess 36', and forms a receptacle with cylindrical forwardly extending walls 40 and bottom wall 41. Centrally contained within primer 39 is anvil 42 which has a conical projection 42' directed rearwardly toward bottom 41. Interposed between anvil 42 and bottom 41 is primer compound 43. Forward sliding movement of primer 39 in a direction away from base 36 is effectively limited by snap ring 44 which fits into groove 45 on the interior of casing 35. The central opening in snap ring 44 serves as a flash port to interconnect the interior of primer 39 with powder charge 46.

Positioned rearward of primer 39 within recess 36' is a lightweight crushable hollow washer 47 formed from polystyrene or a like material which has a large initial volume but a small volume when crushed. Primer piston 48 slideably mounted within the rear portion of recess 36' has forward face 49 in contact with washer 47, and rearwardly directed piston rod 50 slideably mounted in aperture 37. Obturator portion 51 located radially outward of face 49 slideably engages the interior of recess 36'. Radially inward from face 49 is a conical protuberance or anvil portion 52 normally held spaced from bottom 41 of primer 39 by washer 47. Shoulder 48 formed on piston 48 by the connection of rod 50 with face 49 and obturator 51, is normally spaced from shoulder 37' surrounding aperture 37 in base 36 when face 49 is engaged by washer 47. To maintain this position, primer piston 49 is held against rearward movement by staking the base over rear terminus face 53 of rod 50 as indicated at 54. As seen in FIGS. 1 and 3, rear terminus face 53 never projects beyond rear face 22 of cartridge 20 even when shoulder 58' of primer piston rod 50 abuts shoulder 37' of base 36. As a result, the cartridge presents the same outward appearance both before and after firing. By the abovedescribed arrangement, it is seen that forward movement of primer 38 is limited by retaining ring 44. Washer 47 and stakes 54 hold piston 50 fixed to prevent its movement within the casing as the result of g loads applied to the cartridge during shipment and bandling in the firearm before firing. Washer 47 may be eliminated if obturator portion 51 is made slightly oversized so that when the piston is inserted in the cartridge, obturator 51 serves toposition the piston in one location.

In operation, firing pin 30 is driven forward from its position shown in FIG. 1 by conventional means, not shown. Tip 32 enters aperture 37 and contacts face 53 of piston rod 50 driving the same forward until taper 31 abuts bolt recess 24. The initial forward motion imparted to primer piston 48 causes face 49 to crush washer 47 while rigidly seating primer 40 against retaining ring 44.

Continued forward motion causes protuberance 52 to impinge upon the bottom 41 of primer 39. The stroke imparted to piston 48 by the firing pin, and the normal spacing of protuberance 52 from bottom 41 is such that bottom 41 is either pierced by protuberance 52 or is deformed at a rate sufficient to be cracked. In. either event, primer compound 43 is suddenly compressed against the rearwardly directed part 42' of anvil 42 causing initiation of the compound and ignition of charge 46 through the flash port in snap ring 44 whereby propellant gases are produced. Such gases pass rearwardly of primer 39 through theaperture or cracks in bottom 41 and act directly upon forward face 49 of piston 48. These gases thus exert a powerful rearwardly directed force on the piston which serves to drive the piston and firing pin 30 rearwardly since face 53 is in direct contact therewith. Since the gases are free to pass rearwardly of primer 39, adjustment of the diameter of piston 48 can be made-so as to achieve practically any force required to be exerted upon the firing pin.

Primer 39 opens to the interior of the cartridge and the high pressure gases act on both the cylindrical walls 40 and the bottom 41. Walls 40 are obturated into tight frictional engagement with the interior walls of the cartridge defining recess 36'. This frictional engagement retards rearward movement of primer 39 caused by the action of the gases upon bottom 41. Were bottom 41 neither cracked nor penetrated by protuberance 52, piston 48 would be driven rearwardly only by the rearward movement of primer 39. In such case, the net force available is the difference between the total force acting upon bottom 41 and the frictional force arising from the tight engagement of cylindrical side walls 40. While this effect may be tolerated in some instances, greater versatility can be achieved by allowing the gases to pass rearwardly of the primer cup. By this invention, the gases are allowed to act directly upon the piston so that it can move rearwardly directly under the influence of the gases and independently of any movement of the primer.

In order to insure that the primer will remain stationary, the cylindrical walls may be made sufficiently long so that the frictional forceresisting movement of the primer and arising from the gas pressure acting on the walls is greater than the force acting on the bottom which tends to move the primer. However, movement of the primer can be tolerated if the diameter of the rearmost portion of recess 36' in which the piston is slideable is greater than the diameter of the forward portion of recess 36' in which the primer is engaged. Thus, the set-back of the primer could be utilized to allow leakage of gases therepast, which gases would drive piston 48 rearwardly independently of the setback.- In such case, penetration or cracking of the primer may not be necessary.

Since the gases pass behind the primer and act on face 49 of piston 48, it is necessary to seal aperture 37 against'leakage. This is accomplished by providing an obturator rim 51 on the periphery of piston 48. As piston 48 moves rearwardly under the action of the gases, and rim 51 seals the gases internal to the cartridge, face 53 drives firing pin rearwardly. Rearward movement of piston 48 ceases as shoulder 48' contacts shoulder 37. However, the energy already imparted to firing pin 30 is sufficient to cause its continued rearward movement and actuation of the breech mechanism of the firearm.

In a given firearm, with a given mass for the breech mechanism and a desired firing rate, it is possible for those skilled in the art to calculate the energy required to be imparted to the firing pin. Whatever energy is required may be obtained by suitable adjustment to the diameter of the piston with assurance that the provision of direct action of the gases on the piston will result in a uniform amount of energy being imparted to the firing pin from cartridge to cartridge.

The cartridge may be shortened somewhat, and washer 47 eliminated, together with achieving a more simple assembly, by incorporating the primer into the piston. Such embodiment of the invention is illustrated in FIG. 5 which shows primer-piston configuration 60 having forwardly extending cylindrical walls forming a receptacle forprimer compound 43 which is held on disc 61 facing protuberance 52 but spaced therefrom. The forward movement of the receptacle is limited by snap ring'44 in a manner similar to which this element limits movement of the embodiment illustrated in FIGS. 1 through 4. Stakes 54 limit rearward movement of piston 62 in aperture 63. A circumferential groove 40" in walls 40 forms a weakened portion around the periphery at a station just forward of where protuberance 52 is joined to the walls.

In operation, the forward motion of a firing pin upon rear face 64 of rod 62 causes walls 40 to fracture at notch 40" as ring 44 retains the remaining portion of the walls against forward movement. Protuberancc 52 compresses primer compound 43 against ported disc 61 thereby initiating the compound and causing ignition of a charge contained in the cartridge. The propellent gases produced thereby act against the remaining portion of cylindrical walls 40' pressing them into tight engagement with the interior of the recess in the base of the cartridge. The gases also act directly upon the forward face of the piston to drive the same rearwardly independently of the remaining portion of walls 40. The rearward movement imparts the required energy to the firing pin and causes actuation of the breech mechanism. The portion of walls 40' on the periphery of piston remaining after initiation obturate against the surface of the recess in the cartridge and effectively seal aperture 63 against gas leakage.

It should be noted that when shoulder 48 is engaged with shoulder 37 after firing, faces 53 and 64 are interior to the cartridge. This means that the outward appearance of the cartridge is the same after firing as before, so that there is nothing to interfere with the extraction and feed mechanism. Furthermore, it should be noted that discs 42 and 61 serve to limit the forward stroke of protuberance 52 away from the cartridge base, since both discs are in abutting relation to snap ring 44.

Those skilled in the art will now appreciate that this invention contributes a cartridge wherein a primer piston is free to engage and move a firing pin independently of the primer under the' direct influence of propellent gases produced upon initiation of the primer. By such independent movement, frictional forces acting on the primer and arising from the pressure of the propellant gases cannot retard rearward movement of the firing pin.

What is claimed is: y

1. For use with a gun having a firing pin, a cartridge having a hollow casing adapted to contain a'powder charge and having a base at the rear end, said base having an axially extending aperture, a primer mounted in the forward portion of said aperture, retaining means for limiting movement of said primer in a forward direction, a piston slideably mounted in the rearward portion of said aperture behind said primer, said piston having a surface facing said primer, a forwardly extending projection on said surface, said piston adapted to be driven forward by said firing pin causing said projection to strike said primer and deform the same against the resistance of said retaining means, the impact of said projection upon said primer causing initiation of the latter and ignition of the charge whereby propellent gases are produced which act upon said primer and said surface, said piston being rearwardly accelerated independently of said primer by the action of the propellent gases upon said surface to thereby impart a rearward acceleration to said firing pin.

is fired to a rear position where it effects extraction of the cartridge after it is fired, a firing pin movably mounted on said bolt, said firing pin being forwardly movable to a projected position with respect to the bolt when the latter is in forward position, said firing pin being rearwardly movable to a retracted position with respect to the bolt when the latter is in forward position so that continued rearward movement of said firing pin causes said bolt and firing pin to move as a unit until said bolt reaches its rear position, said cartridge comprising a casing containing a powder charge and having a base at the rear end, said base having an axially extending aperture, a primer mounted in the forward portion of said aperture, a piston slideably mounted in the rearward portion of said aperture behind said primer, said piston having a surface facing said primer and a forwardly extending projection on said surface, said piston adapted to be driven forward by said firing pin when the latter moves to projected position to cause said projection to strike and pierce said primer, the striking of said primer causing initiation of the same and ignition of the charge whereby propellent gases are produced, the piercing of said primer allowing a portion of the propellent gases to act upon said surface to rearwardly accelerate the piston, the rearward acceleration of the piston driving said firing pin to retracted position with sufficient energy to cause continued rearward movement of the firing pin whereby the bolt is moved to its rear position.

3. For use with a gun having a firing pin, a cartridge having a hollow casing adapted to contain a powder charge and having a base at the rear end, said base having an axially extending aperture, a primer having walls and a base, said walls being engaged with the forward portion of said aperture, a piston slideably mounted in the rearward portion of said aperture behind the base of said primer, said piston having a surface facing the base of said primer, and a forwardly extending projection on said surface, said piston adapted to be driven forward by said firing pin causing said projection to strike and pierce the base of said primer thereby causing initiation of the latter and ignition of the charge whereby propellent gases are produced, said gases acting upon the walls of said primer to press the walls into tight frictional engagement with the aperture for preventing rearward movement of said primer, said gases also passing through the pierced base of said primer and acting upon said surface to impart rearward movement to said piston.

4. A cartridge comprising a hollow cylindrical casing adapted to contain a powder charge, said casing having a base at one end with an axial aperture therethrough, a primer piston slideably mounted in said aperture for axial movement in one direction toward the charge and in the opposite direction away from the charge, a frangible primer mounted in said aperture between the charge and the primer piston, said primer adapted to be fractured upon axial movement of said piston in said one direction for initiating the primer and igniting the charge whereby propellent gases are produced, said gases passing in said opposite direction through the fractured primer into direct contact with the primer piston for imparting an acceleration thereto in said opposite direction.

5. A cartridge comprising a hollow cylindrical casing adapted to contain a powder charge, said casing having a base at one end with an axial aperture therethrough, a primer piston slideably mounted in said aperture for movement in one direction toward the charge and in the opposite direction away from the charge, a primer mounted in said aperture between the charge and the primer piston, means on said piston to pierce said primer upon axial movement of said piston in said one direction for initiating the primer and igniting the charge whereby propellent gases are produced, said gases passing in said opposite direction through the pierced primer into direct contact with the primer piston for imparting an acceleration thereto in said opposite direction.

6. The cartridge of claim 5 wherein said primer has means responsive to the pressure of the propellent gases for producing a frictional force which impedes movement of said primer in said opposite direction due to the action of said gases. I

7. A cartridge comprising a hollow cylindrical casing adapted to contain a powder charge, said casing having a base at one end with an axially extending cylindrical bore therethrough, a primer piston having a cylindrical surface and a transverse face, the cylindrical surface on said piston being slideably engaged in the bore in said base so that the transverse face on said piston isaxially movable in one direction toward the charge and in the opposite direction away from the charge, and a generally cup-shaped primer having cylindrical side walls and a frangible transverse bottom wall, said primer being mounted in said bore between the charge and the transverse face of the piston with the side walls of said primer engaged with said bore, axial movement of said piston in said one direction causing the face on the piston to engage and fracture the bottom wall of the primer for initiating the primer and igniting the charge whereby propellent gases are produced, said gases passing through the fractured bottom wall of the primer in said opposite direction into contact with the face on the piston for imparting an acceleration thereto in said opposite direction, said gases acting on the side walls of the primer in a radial direction to produce an axial frictional force between the primer and the base that opposes movement of said primer in said opposite direction.

8. The cartridge of claim 7 wherein the primer piston is provided with an obturator seal for preventing leakage of propellent gases past the piston during movement of the latter in said opposite direction.

9. A cartridge comprising a hollow cylindrical casing adapted to contain a powder charge, said casing having a base at one end with an axial aperture therethrough, a primer piston slideably mounted in said aperture for axial movement in one direction toward the charge and in the opposite direction away from the charge, a frangible primer mounted in. said aperture between the charge and the primer piston, stop means to' limit movement of said primer in said aperture in said one direction, and deformable means interposed between said primer piston and said primer for normally preventing said piston from engaging said primer, said piston adapted to be moved in said one direction with sufficient force to deform said deformable means and to engage and fracture said primer for initiating the latter lindrical bore therethrough, and a primer-piston con-' figuration having a piston portion with a transverse face, said piston portion being slideably engaged in the bore in said base so that the transverse face is axially movable in one direction toward the charge and in the opposite direction away from the charge, said configuration having a deformable tubular wall integral with said transverse face and extending therefrom in a direction toward the charge, said tubular wall terminating in a free edge portion, stop means on said casing engaged with said free edge portion for preventing the latter from moving in said one direction upon movement of said piston portion in said one direction, said configuration having an anvil engaged with said stop means for limiting movement of the anvil in said one direction, said configuration having primer compound interposed between said anvil and said face, axial movement of said piston portion in said one direction causing deformation of said tubular walls against said stop means and compression of said primer compound between said face and said anvil, such compression of said primer compound causing ignition of the charge whereby propellent gases are produced in said casing, said gases acting on the face of the piston portion for imparting an acceleration thereto in said opposite direction.

1 l. The cartridge of claim 10 wherein the connection between the tubular wall and said transverse face is frangible, axial movement of said piston portion in said one direction causing said connection to fail whereby said piston portion is separated from said tubular wall and is thrust in said opposite direction by the propellent gases independently of said tubular wall. 

1. For use with a gun having a firing pin, a cartridge having a hollow casing adapted to contain a powder charge and having a base at the rear end, said base having an axially extending aperture, a primer mounted in the forward portion of said aperture, retaining means for limiting movement of said primer in a forward direction, a piston slideably mounted in the rearward portion of said aperture behind said primer, said piston having a surface facing said primer, a forwardly extending projection on said surface, said piston adapted to be driven forward by said firing pin causing said projection to strike said primer and deform the same against the resistance of said retaining means, the impact of said projection upon said primer causing initiation of the latter and ignition of the charge whereby propellent gases are produced which act upon said primer and said surface, said piston being rearwardly accelerated independently of said primer by the action of the propellent gases upon said surface to thereby impart a rearward acceleration to said firing pin.
 2. In combination, a gun having a chamber, a cartridge engaged in said chamber, a bolt on said gun, said bolt being movable from a forward position where it holds the cartridge in the chamber when the cartridge is fired to a rear position where it effects extraction of the cartridge after it is fired, a firing pin movably mounted on said bolt, said firing pin being forwardly movable to a projected position with respect to the bolt when the latter is in forward position, said firing pin being rearwardly movable to a retracted position with respect to the bolt when the latter is in forward position so that continued rearward movement of said firing pin causes said bolt and firing pin to move as a unit until said bolt reaches its rear position, said cartridge comprising a casing containing a powder charge and having a base at the rear end, said base having an axially extending aperture, a primer mounted in the forward portion of said aperture, a piston slideably mounted in the rearward portion of said aperture behind said primer, said piston having a surface facing said primer and a forwardly extending projection on said surface, said piston adapted to be driven forward by said firing pin when the latter moves to projected position to cause said projection to strike and pierce said primer, the striking of said primer causing initiation of the same and ignition of the charge whereby propellent gases are produced, the piercing of said primer allowing a portion of the propellent gases to act upon said surface to rearwardly accelerate the piston, the rearward acceleration of the piston driving said firing pin to retracted position with sufficient energy to cause continued rearward movement of the firing pin whereby the bolt is moved to its rear position.
 3. For use with a gun having a firing pin, a cartridge having a hollow casing adapted to contain a powder charge and having a base at the rear end, said base having an axially extending aperture, a primer having walls and a base, said walls being engaged with the forward portion of said aperture, a piston slideably mounted in the rearward portion of said aperture behind the base of said primer, said piston having a surface facing the base of said primer, and a forwardly extending projection on said surface, said piston adapted to be driven forward by said firing pin causing said projection to strike and pierce the base of said primer thereby causing initiation of the latter and ignition of the charge whereby propellent gases are produced, said gases acting upon the walls of said primer to press the walls into tight frictional engagement with the aperture for preventing rearward movement of said primer, said gases also passing through the pierced base of said primer and acting upon said surface to impart rearward movement to said piston.
 4. A cartridge comprising a hollow cylindrical casing adapted to contain a powder charge, said casing having a base at one end with an axial aperture therethrough, a primer piston slideably mounted in said aperture for axial movement in one direction toward the charge and in the opposite direction away from the charge, a frangible primer mounted in said aperture between the charge and the primer piston, said primer adapted to be fractured upon axial movement of said piston in said one direction for initiating the primer and igniting the charge whereby propellent gases are produced, said gases passing in said opposite direction through the fractured primer into direct contact with the primer piston for imparting an acceleration thereto in said opposite direction.
 5. A cartridge comprising a hollow cylindrical casing adapted to contain a powder charge, said casing having a base at one end with an axial aperture therethrough, a primer piston slideably mounted in said aperture for movement in one direction toward the charge and in the opposite direction away from the charge, a primer mounted in said aperture between the charge and the primer piston, means on said piston to pierce said primer upon axial movement of said piston in said one direction for initiating the primer and igniting the charge whereby propellent gases are produced, said gases passing in said opposite direction through the pierced primer into direct contact with the primer piston for imparting an acceleration thereto in said opposite direction.
 6. The cartridge of claim 5 wherein said primer has means responsive to the pressure of the propellent gases for producing a frictional force which impedes movement of said primer in said opposite direction due to the action of said gases.
 7. A cartridge comprising a hollow cylindrical casing adapted to contain a powder charge, said casing having a base at one end with an axially extending cylindrical bore therethrough, a primer piston having a cylindrical surface and a transverse face, the cylindrical surface on said piston being slideably engaged in the bore in said base so that the transverse face on said piston is axially movable in one direction toward the charge and in the opposite direction away from the charge, and a generally cup-shaped primer having cylindrical side walls and a frangible transverse bottom wall, said primer being mounted in said bore between the charge and the transverse face of the piston with the side walls of said primer engaged with said bore, axial movement of said Piston in said one direction causing the face on the piston to engage and fracture the bottom wall of the primer for initiating the primer and igniting the charge whereby propellent gases are produced, said gases passing through the fractured bottom wall of the primer in said opposite direction into contact with the face on the piston for imparting an acceleration thereto in said opposite direction, said gases acting on the side walls of the primer in a radial direction to produce an axial frictional force between the primer and the base that opposes movement of said primer in said opposite direction.
 8. The cartridge of claim 7 wherein the primer piston is provided with an obturator seal for preventing leakage of propellent gases past the piston during movement of the latter in said opposite direction.
 9. A cartridge comprising a hollow cylindrical casing adapted to contain a powder charge, said casing having a base at one end with an axial aperture therethrough, a primer piston slideably mounted in said aperture for axial movement in one direction toward the charge and in the opposite direction away from the charge, a frangible primer mounted in said aperture between the charge and the primer piston, stop means to limit movement of said primer in said aperture in said one direction, and deformable means interposed between said primer piston and said primer for normally preventing said piston from engaging said primer, said piston adapted to be moved in said one direction with sufficient force to deform said deformable means and to engage and fracture said primer for initiating the latter and igniting the charge whereby propellent gases are produced in the casing, said gases passing through the fractured primer into direct contact with the piston for imparting an acceleration thereto in said opposite direction.
 10. A cartridge comprising a hollow cylindrical casing adapted to contain a powder charge, said casing having a base at one end with an axially extending cylindrical bore therethrough, and a primer-piston configuration having a piston portion with a transverse face, said piston portion being slideably engaged in the bore in said base so that the transverse face is axially movable in one direction toward the charge and in the opposite direction away from the charge, said configuration having a deformable tubular wall integral with said transverse face and extending therefrom in a direction toward the charge, said tubular wall terminating in a free edge portion, stop means on said casing engaged with said free edge portion for preventing the latter from moving in said one direction upon movement of said piston portion in said one direction, said configuration having an anvil engaged with said stop means for limiting movement of the anvil in said one direction, said configuration having primer compound interposed between said anvil and said face, axial movement of said piston portion in said one direction causing deformation of said tubular walls against said stop means and compression of said primer compound between said face and said anvil, such compression of said primer compound causing ignition of the charge whereby propellent gases are produced in said casing, said gases acting on the face of the piston portion for imparting an acceleration thereto in said opposite direction.
 11. The cartridge of claim 10 wherein the connection between the tubular wall and said transverse face is frangible, axial movement of said piston portion in said one direction causing said connection to fail whereby said piston portion is separated from said tubular wall and is thrust in said opposite direction by the propellent gases independently of said tubular wall. 